Safety device for pressurized cabin doors



Dec. 4, 1951 J, CASTLE 2,577,697

SAFETY DEVICE FOR PRESSURIZED CABIN DOORS Filed Nov. 26, 1948 IN VEN TOR.

Jo /Y 645 15- Patented Dec. 4, 1951 UNITED STATES John B. Castle, Los Angeles, Calif., assignor to Douglas Aircraft Company, Inc., Santa Monica,

Calif.

Application November 26, 1948, Serial No. 61,939

8 Claims.

This invention relates to doors, hatches, and similar closures for access openings provided in the enclosed compartments of airplanes and the like, particularly where such compartments'a're pressurized.

Persons have sometimes been lost overboard through the accidental opening of airplane doors because the conventional latch of the ordinar airplane door can be completely retracted from all latching engagement, even if there is no intention of opening the door, by a slight or partial rotation ofv the handle as when it is accidentally contacted or when it is absent-mindedly itoyed" with. Many modern passenger airplanes are pressurized; that is, the interior is at a higher pressure than the external atmosphere when the airplane is flying at high altitudes, and the passenger who accidentally unlatches a door is hence immediately blown overboard through the unlatched, pressure-opened door. Even in unpressurized compartments, if a person happens to be leaning against the door while toying with the handle the door may open, and the passenger will fall or be thrown overboard. Serious accidents have also occurred to members of ground crews attempting to enter pressurized compartments through doors having the conventional latches before the internal pressure has been released from the cabin or reduced to a very lowvalue. Although many airplane doors at present include some sort of manually settable safety device intendedto preclude these occurrences, airplane crews sometimes overlook this detail of servicing so that passengers and ground crews may still undesirably operate the door handle the slight amount necessary to release the pressurized door, with the aforestated disastrous consequences. v v

This invention provides a safety door for vehicles that includes a latch which cannot be completely unlatched, or retracted from all engagement with the door jamb and will hold the door in a partially open position as long as any substantial outwardly acting pressure is exerted against the door itself, no matter how much retractive force is exerted against the door handle or how much the door is pushed. The device prevents the door opening fully until this out- "ward force has been either entirely removed or reduced to such an extent that when the door does open, the passenger contacting it will not be thrown from the vehicle by the air pressure. Similarly, ground crew members atttempting-to enter a. stillpressurized compartment will not be knocked down by a blown-open door or by a sudden rush of air from the compartment. Instead, the device serves as an automatic means for gradually and safely reducing the internal pressure to equalize it with the external pressure.

To achieve these ends, the door, in one of its presently preferred embodiments, essentially includes at least one latch which must be unlatched in two stages. The latch preferably consists of a door bolt member or plunger recoprocatably mounted in the conventional manner in the door to move outwardly and enter a socket in the jamb, its outer end being notched on its outer face to form a detent conformed to, and configured with, a catch member or keeper on the door jamb in such a manner that the bolt or latch member has to be retracted in two stages to release the door. In the first stage of retraction, the operation of a handle disposed on either the outside or the inside of the door withdraws the plunger from its socket in the door frame and fits the detent formation around the stop or catch member, the plunger and door moving outwardly sufficiently to allow the door to crack open and permit the pressure air to gradually escape to approximately the zero level. The outward pressure of this air against the door when the cabin is fully pressurized, may amount to as much as 12,000 pounds on the ordinary sized transport airplane main door, and such pressure positively and securely holds the hook-shaped formation of the plunger against and around the stop so that no amount of manipulation of the handle will further retract the plunger and the door will be in effect locked in its cracked position until the pressure of the air acting thereon and escap ing through the crack falls to a value near zero. The passenger will hear the hiss of the escaping air and feel its action and will desist from his door-opening operations.

After landing, of course, it is safe to go through the second stage of operation of the door and fully retract the plunger from the catch and into the door panel. This action, however, can be performed only after the dangerous air pressure has been reduced. The same situation applies to' personnel on the ground attempting to open the door while the cabin is still pressurized. Only when the pressure is reduced sufficiently can the second stage of operation of the door be performed. These principles can, of course, be applied to rotary and other types of door latches with equal facility.

By way of further clarification and exemplification, only, of the invention andnot as a dispartly in horizontal section, of the invention as embodied in the main door of an airplane, the door handle operating mechanism being merely representationally shown, the latch occupying its first stage in its two-stage unlatching operationto allow the door to crack partly open while securely locking it in that position;

Figure 2 is a fragmentary horizontal section of the door and jamb with the door closed and hermetically sealed and the latch shot home into its socket;

Figure 3 is fragmentary horizontal sectional view of the door and janib with the door locked ajar to exhaust the pressure air, the latch being partially retracted to occupy its first position in the two-stage unlatching operation;

Figure 4 is a similar section showing the door with the latch in the second stage of the unlatching operation, the pressure having been removed from the door and the plunger having been freed and fully retracted, enabling the door to be fully opened; and,

Figure 5 is a fragmentary diagrammatic perspective of a pressurized airplane cabin provided with pressurizing means, pressure air outflow controlling means, and a passenger door incorporat 1 ing the invention. I M

In all its embodiments and for any type of door the invention essentially includes at least one latch, including a movable latch bolt, detent, and catch configuration for each door. For. pressurized airplane doors such as those shown in the drawings the number of such latch units may be suitably increased, the units being properly disposed at spaced points around the periphery of the door.

The illustrated embodiment comprisesv a door If], framed in the conventional airframe manner and hinged to the fuselageshell I00 along its one edge for opening outwardly. Asource of pressure-air IOi, such as a conventional cabin-pressurizing supercharger, mounted in the usual 4 manner in the adjacent wing, not shown, and driven by an adjacent engine, not shown all in the conventional manner, supplies pressure air to the fuselage. A cabin pressure control valve I02 is adapted to open and close automatically to maintain the cabin pressure at preselected values. Adjacent the edge opposite the hinged edge of the door the fuselage shell includes a door jamb II. In orderto hermetically seal the door to the fuselage of the pressurized compart ment of the aircraft, a seal 12, comprising a resilient strip mounted in a suitable channel, is disposed around the periphery of the door panel and an air pressure retainer angle I3 is disposed around the inner periphery of the door jamb and cooperates with the resilient strip to prevent air flow outwardly. The shell liner member Am the interior of the door jamb is provided with a socket or passage l4 and the inner face of the door jamb plating or skin bears an apertured bracket 15 which takes the retainer strip loads and bears a forwardly extendingarm I512. Acorrespondingly apertured bracket lfi is mounted on the outside ofthe adjacent edgeo'f the door-panel with the. two apertures longitudinally aligned.

A series of door latching plungers or bolts like that which is designated H is reciprocatably disposed in the door panel, each bolt lying in alignment with one of the aforesaid apertures, and each latch member is adapted to be slid into and retracted out of same, the inner end of the member llbeing slidably mounted in a stabilizing bracket i8 which carries 7 anti-friction guide rollers 59 spacedly mounted in the one end thereof and engaging the inner end of the plunger. Below the plunger is disposed plunger operating means representationally shown as a shaft 2| terminating at each end in an operating handle, not shown, for opening the door from the inside and the outside. Substantially medially of the length of this shaft is pinned a vertically extending crank 22 terminating upwardly in a fork 23-, each check of which bears a vertically extending slot 24. The inner end of the plunger I1 is extended in the form of a bi-armed member 25, the arms 2c of which work in the slots 24 to accommodate the rise and fall of the member 22 when the shaft 2! is rotated to reciprocate the plunger 11.

A vertically extending anti-friction guideroller 2? is rotatably mounted on the inner end of bracket I6 adjacent to the inner vertical face of the plun-ger'in guiding and restraining relationship thereto but spaced away therefrom in the direction towards the interior of the fuselage. A similar roller "28, serving as a keeper. is mounted on the outer end of the arm 15a to depend vertically therefrom into parallel tangency with the outer vertical face of the plunger when the plunger is in the Figure 2 position. An arm similar to member I5a supports the lower end of roller 28. By this arrangement,the plunger is adapted to be reciprocated from the position shown in Figure 2fto the position of Figure 4, moving in a supported and guided manner, serving to latch the door closed when shot home into the socket region It and freeing the door for full opening when fully retracted into the position shown in Figure 4.

Inorder to prevent full opening of the door when operating force is" applied to either handle while air pressure is acting thereon or someone is leaning against it, means are provided for causing the door to unlatch in two stages, the first stage of retraction of the latch from its jamb socket into engagement with a stop enabling relief of the pressure on the door while preventing the complete retraction of the plunger ll from all engagement with the door jamb and locking the door in partially open position until said pressure or outwardly acting force is removed from the door. The second stage, consisting of completing the retraction of'the plunger to allow full opening of the-door, can only be performed when practically all outward pressure has been removed from the'door, no matter how much torque force is applied to the handles.

To these ends, the outer vertical face 29 of the active end portion of the plunger ii, in a region disposed near or just outwardly of the region where, in the latched condition, this'face contacts the roller 28 is conformed to substantially a hook-shape to constitute a catch member con-'- gruent with the adjacent surface of the roller member 28. That is to say, this face is reentrantly so shaped in this region as to define a notch 32, the forward Wall 36' of which is more acutely ire-entrant than the rearward wall 3! so as to provide a massive, deep, stress taking. por-- tion outwardly of the notch, at the same time being so shaped as to'easily cam over and overammo? ride the roller 28 when the plunger is fullyreitracted after de-pressurizing. The wall 3| has a slope gradual and deep enough to enable" the plunger tomove-outwardly so that the door can crack .open enough to vent the air when' the first stage of unlatching-is' initiated Thus when the door handle is turned, instead of the door being violently fiung open and the passenger being blown or thrown overboardfthe plunger locks on the jamb in theposition of Figure 3, beingheld there by the outwardpressure onthe door with the catcher hook portion thereof engaged around the detent or roller, the door coming partiallyopen and venting the pressure air. .As long'as there is any danger, the plunger cannot be retracted further, no :matter .how much effort is applied to the handle.- Also, although the pressure air vvents through the crack, not enough air escapes at one time to blow .over anyone adjacent thedoor on the ground and attempting to open the pressurized door, nor will large loose objects in the fuselage be blown onto him. v i

When the force acting outwardly on the door .is removed or sufficiently reduced, however, the handle can be turned and the plunger willride over the roller and retract into the door.

Various other structural shapes and arrange ments than the particularones illustrated may be employed to achievethe same endswithout partment above ambient atmospheric "pressure and including an aperture in'the outer wall of said compartment and a panel member mounted in sealing relation in said aperture for-outward opening, safety latch mechanism comprising: fixed 1am means carried by said wall; latch means carriedby said panel member and movable, in the general plane of said panel "member, in one direction to release said panel member for opening and in another direction to a position inwardly of saidlfixed latch means to retain said panel member in closed, sealing relation; said movable latch means having an outwardly facing, engageable surface provided toward its free end with a depression and with a first detent portion nearer to said free end and defining the outer limit of said depression; said fixed latch means'having a second detent portion "extending toward said engageable surface and adapted to contact successive portions thereof and to' seat in said depression upon predetermined partial withdrawal of said movable latch means to prosure airflow into and out of'said compartment and to maintain the air pressure within said compartment above ambient atmospheric pressure and including an aperture in theouter wall of'said compartment and a panel member mounted in sealing relation in said aperture'for out ward opening, safety latch mechanism comprising: latch means carried by said wall and said panel member; one of said latch means being movable with respect to the other, in the general plane of said wall and said panel member, in one direction to release said panel member for opening and in another direction to retain said panel member in closed, sealing relation, with the latch means carried by said panel member 10-.

catedinwardly of the latch means carried by said wall; a-fir'st one of said latch means having a first detentportion extending toward the other latch means; the second one of said latch means having 'anengageable surface facing toward said first detent portion for engagement thereby-at successive portions of said surface and terminating in a depression; said first detent portion being adapted to seat in said depression uponpartial disengagement of said'latch means to provide for partial opening of said panel member and escape of pressure air from said compartment; a second detent portion forming the outer limit of said depression at a side oppositetosaid engageable surface and adapted to abutsaid first detent portion when thelatter is seated. in :said depression and to overlap it in a direction substantially normal to the direction. of relative movementof said latch means and thereby prevent full disengagement thereof; said detent portionsbeing movable past each other only upon inward movement of said panel member. f

3. Safety latch mechanism for an aircraft compartment having'a wall structure provided with'an aperture therein and a door mounted in said aperture for opening in an outward direction in response to pressure applied to the inner side thereof, comprising: relatively movable interengaging latch means on said door and said wall structure movableto engaged relation to restrain said door against opening and movable to disengagedrelation to release said door for opening;

a first one of said latch means having an elongate engaging'surface thereon; a second one of said latch means having a detent portion extend-'- ing toward said surface to engage successive portions thereof and positively prevent opening of said'door; and second detent means on said first latch means extending in the direction of said second latch means to'laterally overlap said first detent means and engage therewith in interfering relationship to prevent full disengagement of said two'latch means; said detent means being laterally movable with respect to each other for disengagement thereof and full disengagement of said latch means only after movement of said door in a direction opposite to its direction of opening.

4. Safety latch mechanism for an aircraft compartment having a structure including a wall with an aperture therein, and a door movable outward to open said aperture and inward to close said aperture, comprising: relatively movable interengaging latch means on said door and said structure, the latch means on said structure being located generally outwardly of the latch means on said door when they are interengaged;

a first one of said latch means having an elongate engaging surface facing toward the second one; ofqsaid latch: means and terminated by-a first detent portion; the second. one, of said. latch means; having a second detent portion extending toward. said surface to engage successive portions thereof and positively prevent opening. of said door; said detent portions being adapted to abut and: interfere with each other uponpartial disengagement of saidv latch means; the innermost partof the detent portion carried by said structure lying'inwardly of the outermostv part of. the detent; portion carried by said door when said detent, portionsare in such interfering, abutting relation; whereby said door must. be moved inwardly'before said latch means, can be fully disengaged tov release said door for opening.

Safety latch mechanism for an aircraft compartmenthaving a structure including a wall tively preventing full.v disengagement of. said with an aperture therein, and a door movable gate engaging surface facing towardthe second one. of said latch means carried by saiddoor; latch means carried by said structure located generally outwardly of the latch means carried by'said door-when saiddoor is fully closed; said latchmeans .being movable relative to each other in: a direction generallyparallel to the general plane. of said door; a detent portion on each of said latch means adapted to abut each other when said latch means are. partially disengaged andto overlap each other ina direction substantially at right angles to the plane of the door whenjn such abutting relation to prevent full disengagement. of said latch means.;, said door and its latch means being, movable inwardly to an extent sufiicient to eliminate the overlap between. said detent portions and permitfull dis'- engagement of said latch means andopening of said door.

6. Safety latch mechanism for an aircraft compartment having a structureincluding awall with an. aperture therein, and adoor movable outward to open said aperture. and inward to close said aperture, comprising; relativelyrnovf able. interengaging latch .means on said door and said structure, the latch means on said structure being located generally outwardly of the latch means onsaid door when they are interengaged; a first one of said latch means havingan elongate engaging surface facingtowardithe second one of said latch means; the second one of said latch meanshaving a first detent portion extend-.- 'ing toward said surface tofe'ngage successivepore tions. thereof and positively prevent opening of said door; a second detent portion on sa'idfirst latch means extending toward said second-latch means and lying in interfering relation with the path of movement of said first detent portion as it moves relatively in the direction of. disengagement of said'latch means in contact with said latch; means;v said: detent-portions being" movable out of interfering abutting; relation onlyby movement of said: door in a direction opposite to its direction of opening.

7.1m an aircraft. of the type having a pressurizedzcompartmenta'nd means to providepressure airflow into and out of said compartment and to. maintain. the air pressure. within said compartment. ab'oveambient. atmosphericv pres.- sure andincludingan aperture in the. outer wall of said compartment. and a panel: member mounted in sealing; relation in said aperture for outward opening, safety latch and depressurizing. mechanism: comprising: relatively movable latch means carried by said walland said panel member; first, second, and; third engageable means. on .a first one. of said. latch .means; and: a member. on; a second one of. saidlatch means engageable. with saidfirst engageable means to hold said panel member in sealing relation, with said second engageable means to hold said panel member in'partly opened'position to release pressure air from said compartment, and with said thirdengageable meansto positively prevent full disengagement of said latch means; said memher. being; disengageable from said. third. means for fulldisengagement. of said latch means. only upon movement of. said panel member in a direction opposite to itsdirection of opening.

3. Safety latch. mechanism for an aircraft compartment. having'a structure including a wall with an aperture therein, and a door movable outward to open said aperture and inward to close said aperture, comprising: relatively movable latch means carried by said wall and said door; first and second engageable means on a first one of. said latch means; and amember on asecond oneof said latch means engageable with said first engageable means to positively prevent opening of said. door, and with said second engageable means to positively prevent full disengagementof said-latch means; said member being disengageable from said second means for full disengagement of. saidlatch means only upon movement of said door. in a direction opposite to itsdirection of opening.

' JOHN B. CASTLE.

REFERENCES CITED The following references are of record in the file of this patent: 

